Bio Class 10 - Muscular, Skeletal, and Respiratory Systems

What are general characteristics of skeletal muscles? Control, location, nuclei, microscopic appearance

Voluntary

On the bones

Multinucleate

Striated under microscope

What is the hierarchy of muscle cells?

Protein filaments (actin and myosin) → sarcomere → myofibril (organelle) (string of sarcomeres) → muscle cell (myofibers) (bundle of myofibrils) → fascicle (bundle of muscle cells) → whole muscle (bundle of fascicles)

What are parts of a muscle cell?

Myofibrils, mitochondria, sarcoplasmic reticulum, T-tubules, mitochondria, nuclei

What is the SR?

Sarcoplasmic reticulum

Storage of calcium in muscle cells

What are T-tubules?

Invaginations of muscle cell plasma membrane

Allows action potentials to travel to the interior of the cell

What gets shorter when muscles contract?

Sarcomere and larger get shorter

Proteins (actin and myosin) themselves do not

How are sarcomeres structured?

Ended on either side by Z-lines

Actin (thin filament) attached to Z-lines

Myosin filaments (thick filaments) overlap with actin

I-band: where only actin and Z-line is

A-band: myosin and actin

H-zone: only myosin

Why do skeletal muscles look striped

H band and I band are lighter in color → alternates with A-band, which is darker → striped

What is the sliding filament theory? 4 steps.

1. Myosin heads bind to actin filaments

2. Myosin pulls actin towards center of the sarcomere

3. Myosin releases actin

4. Myosin resets to high energy conformation

How does myosin bind to actin?

Called “cross-bridge formation”

Uses calcium

Not all myosin heads bind and release at once → net movement only happens when some myosins are attached to actin

How does myosin pull actin towards the center of the sarcomere?

AKA “power stroke”

Uses no ATP

Myosin returns to low energy state

How does myosin release actin?

Requires ATP to be present

How does myosin reset to its high energy form?

Requires hydrolysis of ATP

What is the part of muscle contraction first affected by a lack of ATP?

Muscle relaxation → why there is rigor mortis

What is the thin filament? How is it structured?

Actin, tropomyosin, troponin

Actin forms bundles → tropomyosin covers myosin binding sites on actin → troponin sits on top of tropomyosin and binds Ca²⁺

What is excitation-contraction coupling?

Excitation: muscles innervated by neurons → action potentials → depolarization of muscle cell → open calcium channels in the SR → calcium released into cytosol

Contraction: troponin binds to calcium → pulls tropomyosin off of myosin binding site → myosin binds to actin → sliding filament theory picks up here

Why does contraction of muscle cells require so much ATP?

Must use active transport to get calcium out of cytosol and back into SR

Sliding filament theory uses ATP to relax muscles

What are motor units?

Neurons and all of the muscle cells it controls

All muscle cells in a motor unit contract as one

Large: 1000s of muscle cells per neuron

Small: 10-20 muscle cells per neuron

How are muscle contractions controlled in a graded fashion (how do you contract strongly vs softly)?

Contract different numbers of motor units

More = stronger

How is gross motor control innervated?

A few large motor units

How is fine motor control innervated?

Many small motor units

How does your body know how many motor units to use for movements?

This is what you learn as a baby

Or by practicing motor movements

What are sources of ATP for muscles? From fastest to slowest.

Creatine-P + ADP → creatine + ATP

Glycolysis: 2 net ATP, lactic acid

Aerobic metabolism: 30 ATP, CO₂, H₂O

In very long-term movements, switch between aerobic and glycolysis

What is myoglobin?

Stores one oxygen

In muscles that are used for super long-term endurance

Allows for aerobic respiration

Myoglobin is dark, makes dark meat

What is oxygen debt?

Extra oxygen needed after exercise to replenish oxygen stored on myoglobin and convert lactic acid into something useful

Why is oxygen required to convert lactic acid to something useful?

Must be oxygenated back to pyruvate first → to do other things with it requires ATP → need oxygen to make ATP

Where does the oxygen come from to repay the oxygen debt?

Pull more oxygen off of hemoglobin

Increased CO₂, increased temperature, and decreased pH shift hemoglobin curve right → this stuff happens when exercising (Bohr conditions) → Hb has a lower affinity to oxygen

These conditions do not shift in lungs due to oxygen

What are types of skeletal muscles?

Slow twitch

Type IIA

Type IIB

What are slow twitch muscle characteristics? AKA, myoglobin content, capillary network, speed of contraction, # of mitochondria, fatigue resistance, force generated, example

AKA: slow oxidative fibers

Myoglobin content: high

Capillary network: very dense

Speed of contraction: slow

# of mitochondria: high

Fatigue resistance: high

Force generated: low

Example: thigh muscles of marathon runners

What are type IIB skeletal muscle characteristics? AKA, myoglobin content, capillary network, speed of contraction, # of mitochondria, fatigue resistance, force generated, example

AKA: fast twitch

Myoglobin content: none

Capillary network: very few

Speed of contraction: very fast

# of mitochondria: very low

Fatigue resistance: low

Force generated: high

Example: thigh muscles of sprinters

What are type IIA skeletal muscle characteristics? AKA, myoglobin content, capillary network, speed of contraction, # of mitochondria, fatigue resistance, force generated, example

AKA fast oxidative

Myoglobin content: low

Capillary network: medium

Speed of contraction: medium

# of mitochondria: some

Fatigue resistance: medium

Force generated: medium

Example: thigh muscles of 5k runners

What are characteristics of cardiac muscles? Function, location, nuclei, microscopic appearance

Involuntary, autorhythmic (can generate own contraction)

Only in the heart

Uninucleate

Striated

How does the functioning of skeletal and cardiac muscle contractions differ?

Skeletal: calcium comes exclusively from SR

Cardiac: calcium from both SR and extracellular environment

What are characteristics of smooth muscles? Function, location, nuclei, microscopic appearance

Involuntary, neurally stimulated, hormonally stimulated, mechanically stimulated

Walls of hollow organs

Uninucleate

Non-striated

What is connective tissue?

Lots of extracellular material, but not many cells

Cells in a matrix

Connects other tissues

What types of cells are in connective tissues?

“___ blast”

“____ cyte”

What are fibroblasts?

Generic connective tissue cells

What are “____ blast” cells?

Immature cells

Still divide

Produces the matrix of connective tissue

What are “____ cyte” cells?

Mature cells

Usually do not divide

Maintain connective tissue matrix

What is the matrix of connective tissue made of?

Fibers and glop (ground substance)

What are fibers and their roles in connective tissues?

Collagen: strength (triple helix protein → super strong)

Elastic: recoil (regain shape after stretch)

What is the glop (ground substance) in the connective tissue matrix?

Liquid (blood plasma)

Solid (bone)

Can be anywhere between bone and liquid

What is the main role of connective tissue?

Plays a supporting role

What are four functions of the skeletal system?

Support and movement

Protection

Blood cell formation

Mineral storage of calcium and phosphate

What is the anatomy of long bones?

Well defined shaft (diaphysis)

Two well defined ends (epiphysis)

What is the anatomy of the diaphysis?

Medullary cavity filled with yellow bone marrow (fat)

Compact bone (relatively non-porous and inflexible)

Osteons surround medullary cavity

What is the structure of an osteon?

Central canal with blood vessels, nerves, some fat

Bone grows around central canal in rings

Osteocytes all along rings (dormant cells)

How do osteocytes get nutrients?

Have a cavity system that connects them to each other and back to the central canal

Called canaliculi

Joined by gap junctions

What is bone made of?

Solid calcium phosphate matrix

What is the anatomy of the epiphysis?

Outer shell is compact bone

Inner core is spongy bone (more porous and flexible)

Spongy bone is made of red bone marrow (blood cell formation)

What is the epiphyseal plate?

Cartilage between epiphysis and diaphysis → can grow and push them apart to allow for bone growth → rate of ossification is larger than rate of growth → ultimately your bones are all bone

What does parathyroid hormone do?

Increases blood calcium

Stimulates bone breakdown (osteoclasts dissolve bones)

Increased absorption of calcium in intestines

Increases reabsorption of calcium in kidneys

Can do calcium regulation on its own if it needs to

What does calcitonin do?

Decreases blood calcium

Stimulates bone formation (osteoblasts build bones)

Decreases absorption of calcium in intestines

Decreases reabsorption of calcium in kidneys

What are the functions of the respiratory system?

Gas exchange

pH regulation (fast)

What is ventiallation?

Moving air in/out of a system

What is respiration?

Gas exchange

Where does respiration happen? What do you call each?

Between lungs and blood = external

Between blood and body cells = internal

What do the organs of the conduction zone do?

Ventilation

What organs are in the conduction zone?

Nose/nasal cavity

Pharynx

Larynx

Trachea

Primary bronchi, secondary bronchi (lobar) → → → terminal bronchioles

What is the role of the nose/nasal cavity?

Warms air

Humidifies air

Filters air

What is the structure of the nose/nasal cavity?

Lined with respiratory epithelium and mucus cells

Lots of cilia that can push mucus (and stuff trapped within it) out

What are the parts of the pharynx? What they do? What are they lined wiht?

Nasopharynx (behind nose): moves air, lined with respiratory epithelium

Oropharynx (behind mouth cavity): lined with protective layers of cells

Laryngopharynx (behind larynx): moves air and food, lined with protective layer of cells

What is the role of the larynx? Made out of?

Made entirely of cartilage (so trachea does not collapse)

Keeps trachea open, separates food and air (controls epiglottis), voice production

What does the trachea do? Structure?

Alternating bands of cartilage and connective tissue membrane

Trachealis muscle controls the diameter

What is the structure of the bronchi and bronchioles?

Primary bronchi have rings of cartilage, no smooth muscle → as you go to second → plates of cartilage and some smooth muscle → as you move past tertiary → no cartilage, all smooth muscle

Start off lined with tall cells with cilia → eventually go to short cells with no cilia

How are secondary bronchi and below controlled?

Sympathetic nervous system relaxes the muscles → more air

Epinephrine is the major hormone of the SNS → relaxes muscles → why epipen injections open airways

Inhalers work similarly

What are the organs of the respiratory zone?

Bronchial tubes (respiratory bronchioles that branch off of terminal bronchioles of conduction zone)

Alveolar ducts

Alveolar sacs

Alveoli

What is the structure of alveoli?

Made of super thin cells for easy diffusion (type I cells)

Have some type II cells lining them

What do type II cells do in alveoli?

Produces surfactant

Reduces surface tension inside alveolus → so alveoli can be separated again if they contact one another

Makes breathing easier

What is the structure of respiratory bronchioles?

All smooth muscle

Includes some alveoli so it can do gas exchange

What is the alveolar duct?

Connects respiratory bronchiole to alveolar sac

What are alveolar sacs?

Surround an alveolus

How are alveoli expanded/contracted?

Alveolar sac stuck to side of chest cavity → change size of chest cavity → change size of alveolar sac, thus alveoli

How is ventilation controlled?

Lungs stuck to inside of chest cavity → expand chest cavity → expand lungs → air comes in → contract chest cavity → contract lungs → air goes out

Why are lungs stuck to the chest cavity walls?

Surface tension

Slight negative pressure in the space between lungs and chest wall → lungs and chest wall push together

Losing negative pressure → cannot breathe

What is inspiration? Relaxed expiration? Forced expansion?

Inspiration (active): diaphragm contracts down → increase size of chest cavity → pressure decrease in lungs → air in

Relaxed expiration (passive): relax diaphragm → lungs elastically recoil → decrease size of chest cavity → pressure increases → air out

Forced expiration (active): contract abdominal muscles → increased pressure in abdominal cavity → diaphragm pushed up past resting position → air forcefully pushed out

What is ventilation rate based on?

Need to regulate pH

Ventilation increases pH → why we breathe faster after exercise

Cell functions decrease pH

What are the three layers of the skin? What are they made of?

Epidermis: epithelial tissue

Dermis: connective tissue

Hypodermis: fat

How does skin help with thermoregulation?

Cold: deactivate sweat glands, shivering, vasoconstriction

Hot: activate sweat glands, no shivering, vasodilation